Add hook in CameraApp to register a RemoteShutterListener.

Builds can provide an implementation of RemoteShutterBridge whose
create method returns a more interesting implementation of a
RemoteShutterListener. This also removes the need for the NOOP
RemoteShutterListener constant; instead, the default implementation of
RemoteShutterBridge returns the NOOP listener.

Change-Id: I5ec381abbb3fa5e38249f8a77edc765083bf32aa
3 files changed